1. Field of the Invention
The present invention relates to a control apparatus for an internal combustion engine, and, in particular, to a control apparatus for an internal combustion engine that is used to control a four-stroke engine serving as an internal combustion engine.
2. Description of Related Art
In a batteryless vehicle which travels by an internal combustion engine, electric power which is required at startup is fully provided by generated power from a generator that is driven by the rotation of the crankshaft of the internal combustion engine.
Because of this, it is necessary to complete startup control using limited power.
Accordingly, when a batteryless vehicle is being started up, it is desirable for power consumption to be kept as low as possible.
Techniques to control the startup of a conventional batteryless vehicle are the techniques described in (1) and (2) (see below) in which power consumption is controlled so that startability is guaranteed.
(1) A technique is disclosed in Japanese Patent No. 3201684 in which, in a batteryless vehicle, a switch is provided that is used to start or stop the supply of generated power to loads other than ignition, and the opening and closing of this switch is controlled in accordance with the engine speed.(2) A technique is disclosed in Japanese Unexamined Patent Application, First Publication No. 2004-360631 in which, in a batteryless vehicle that employs a DC-CDI (i.e., a condenser discharge type) ignition system, when a power supply voltage that is supplied by a generator increases to a predetermined value (i.e., a booster operation permitting voltage), then a booster operation of the condenser voltage is started using a DC converter of the DC-CDI ignition system.
Among internal combustion engines that are started by manual cranking, for example, four-stroke single-cylinder engines, internal combustion engines exist that are only able to be cranked approximately three revolutions in a single startup operation.
In this type of internal combustion engine, it is essential in order to ensure startability for ignition to take place at the top dead center of the initial compression.
However, as described above, the power supply of an ECU (Engine Control Unit) of a batteryless vehicle is supplied from a generator that is driven by the rotation of a crankshaft.
Because of this, when the boosting of a condenser of a DC-CDI ignition system is started, the power supple voltage is reduced, and the problem sometimes arises that the power supply voltage drops below the minimum operating voltage of the CPU (Central Processing Unit) inside the ECU, so that the functions of the ignition system are stopped and the ignition opportunity at the top dead center of the initial compression is lost.
In order to avoid such problems, consideration has been given to increasing the capacity of the generator. However, this solution is not preferable as it tends to lead to an increase in both the size of the generator and the cost thereof.
In the technique disclosed in Japanese Patent No. 3201684, no switch is provided in order to start or stop the supply of generated power to the ignition system. Because of this, when this system is applied to a fuel injection system, there is insufficient ignition output due to CPU voltage reduction.
Moreover, when the ignition system disclosed in Japanese Unexamined Patent Application, First Publication No. 2004-360631 is applied to a fuel injection system, startup is not possible unless fuel injection is given precedence and is performed prior to ignition output.
Because of this, unless consideration is given to both voltage reduction that is caused by the fuel pump and the injector being driven and voltage reduction that is caused by the operation to boost the condenser voltage performed by the DC converter, then it is not possible to set a voltage booster operation permitting voltage.
Moreover, it is difficult to avoid a reduction in the CPU voltage simply by setting an permitting voltage for the supply of power to each device such as the ignition system, the fuel pump, and the injector, and the possibility remains that this will deteriorate into a situation in which startup is not possible.